The present invention relates to video-on-demand systems which send multiple streams of video data from a video library to respective sets of viewers. More specifically, the present invention relates to methods of testing video servers in the above video-on-demand systems.
In the prior art, one video-on-demand system is described in U.S. Pat. No. 5,583,561 which is entitled “Multi-Cast Digital Video Server Using Synchronization Groups”. An overview of this prior art system is shown in FIG. 1 of patent '561. There, multiple videos are stored in a video library 10 which is coupled to a video server 12; and, the video server 12 is coupled through a network interface circuit 18 and a distribution network 20 to a plurality of video display devices 24 and 26.
To receive a particular video at a particular display device, a request is sent to the video server by a viewer at the display device. This request is sent by means of a control terminal which is coupled to a communication channel that feeds back to the video server. The control terminal in FIG. 1 is a touch-tone telephone; but as an alternative, the control terminal can be a personal computer, or special purpose hardware similar to a handset for remotely controlling a VCR. This is explained at lines 35-45 in column 7 of patent '561.
In response to a viewer's request for a particular video, the video server 12 reads the requested video from the video library 10. Thereafter, that video is sent as a stream of video data from the video server 12 through the network interface circuit 18 to the particular display device that is paired with the control terminal from which the video was requested.
One method for passing the stream of video data from the video server 12, through the network interface circuit and distribution network, to the display device is disclosed in detail in patent '561. Also, an alternative method is disclosed in a pending patent application which has Ser. No. 09/318,987 and is entitled “Scalable Video System Having Shared Control Circuits for Sending Multiple Video Streams to Respective Sets of Viewers”. All of the details in the above patent and patent application are herein incorporated by reference.
While a stream of video data is being sent from the video server to a particular display device, the control terminal for that display device provides a means for sending various VCR-like commands back to the video server. These VCR-like commands include commands such as PAUSE, STOP, PLAY, REWIND or FAST FORWARD. In response, to implement each VCR-like command, the video server 12 performs various steps on the video stream which it is sending to the particular display device. This is illustrated in FIG. 8 of patent '561.
Now, a problem which arises when a new video server is being designed is how to test and check-out the operation of the video server. The direct way to perform such a test is to first build the entire video-on-demand system, and then have viewers at each display device who send the VCR-like commands to the video server through the control terminals for the display devices.
However, a major drawback of the above direct testing method is that the cost to build the entire video-on-demand system can be very large. This large cost occurs in part, because dozens or even hundreds of display devices and control terminals can be coupled to the video server via the distribution network and the feedback communication channel. But, to fully test the video server, it should be tested to its maximum capability.
Accordingly, a primary object of the present invention is to provide a method of testing a video server for a video-on-demand system which is very economical and completely avoids the above problem.